1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/fs.h> 31 #include <linux/nsproxy.h> 32 #include <linux/capability.h> 33 #include <linux/cpu.h> 34 #include <linux/cgroup.h> 35 #include <linux/security.h> 36 #include <linux/hugetlb.h> 37 #include <linux/seccomp.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/futex.h> 42 #include <linux/compat.h> 43 #include <linux/kthread.h> 44 #include <linux/task_io_accounting_ops.h> 45 #include <linux/rcupdate.h> 46 #include <linux/ptrace.h> 47 #include <linux/mount.h> 48 #include <linux/audit.h> 49 #include <linux/memcontrol.h> 50 #include <linux/ftrace.h> 51 #include <linux/proc_fs.h> 52 #include <linux/profile.h> 53 #include <linux/rmap.h> 54 #include <linux/ksm.h> 55 #include <linux/acct.h> 56 #include <linux/tsacct_kern.h> 57 #include <linux/cn_proc.h> 58 #include <linux/freezer.h> 59 #include <linux/delayacct.h> 60 #include <linux/taskstats_kern.h> 61 #include <linux/random.h> 62 #include <linux/tty.h> 63 #include <linux/blkdev.h> 64 #include <linux/fs_struct.h> 65 #include <linux/magic.h> 66 #include <linux/perf_event.h> 67 #include <linux/posix-timers.h> 68 #include <linux/user-return-notifier.h> 69 #include <linux/oom.h> 70 #include <linux/khugepaged.h> 71 #include <linux/signalfd.h> 72 #include <linux/uprobes.h> 73 74 #include <asm/pgtable.h> 75 #include <asm/pgalloc.h> 76 #include <asm/uaccess.h> 77 #include <asm/mmu_context.h> 78 #include <asm/cacheflush.h> 79 #include <asm/tlbflush.h> 80 81 #include <trace/events/sched.h> 82 83 #define CREATE_TRACE_POINTS 84 #include <trace/events/task.h> 85 86 /* 87 * Protected counters by write_lock_irq(&tasklist_lock) 88 */ 89 unsigned long total_forks; /* Handle normal Linux uptimes. */ 90 int nr_threads; /* The idle threads do not count.. */ 91 92 int max_threads; /* tunable limit on nr_threads */ 93 94 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 95 96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 97 98 #ifdef CONFIG_PROVE_RCU 99 int lockdep_tasklist_lock_is_held(void) 100 { 101 return lockdep_is_held(&tasklist_lock); 102 } 103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held); 104 #endif /* #ifdef CONFIG_PROVE_RCU */ 105 106 int nr_processes(void) 107 { 108 int cpu; 109 int total = 0; 110 111 for_each_possible_cpu(cpu) 112 total += per_cpu(process_counts, cpu); 113 114 return total; 115 } 116 117 void __weak arch_release_task_struct(struct task_struct *tsk) 118 { 119 } 120 121 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 122 static struct kmem_cache *task_struct_cachep; 123 124 static inline struct task_struct *alloc_task_struct_node(int node) 125 { 126 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node); 127 } 128 129 static inline void free_task_struct(struct task_struct *tsk) 130 { 131 kmem_cache_free(task_struct_cachep, tsk); 132 } 133 #endif 134 135 void __weak arch_release_thread_info(struct thread_info *ti) 136 { 137 } 138 139 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR 140 141 /* 142 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a 143 * kmemcache based allocator. 144 */ 145 # if THREAD_SIZE >= PAGE_SIZE 146 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 147 int node) 148 { 149 struct page *page = alloc_pages_node(node, THREADINFO_GFP, 150 THREAD_SIZE_ORDER); 151 152 return page ? page_address(page) : NULL; 153 } 154 155 static inline void free_thread_info(struct thread_info *ti) 156 { 157 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 158 } 159 # else 160 static struct kmem_cache *thread_info_cache; 161 162 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, 163 int node) 164 { 165 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node); 166 } 167 168 static void free_thread_info(struct thread_info *ti) 169 { 170 kmem_cache_free(thread_info_cache, ti); 171 } 172 173 void thread_info_cache_init(void) 174 { 175 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE, 176 THREAD_SIZE, 0, NULL); 177 BUG_ON(thread_info_cache == NULL); 178 } 179 # endif 180 #endif 181 182 /* SLAB cache for signal_struct structures (tsk->signal) */ 183 static struct kmem_cache *signal_cachep; 184 185 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 186 struct kmem_cache *sighand_cachep; 187 188 /* SLAB cache for files_struct structures (tsk->files) */ 189 struct kmem_cache *files_cachep; 190 191 /* SLAB cache for fs_struct structures (tsk->fs) */ 192 struct kmem_cache *fs_cachep; 193 194 /* SLAB cache for vm_area_struct structures */ 195 struct kmem_cache *vm_area_cachep; 196 197 /* SLAB cache for mm_struct structures (tsk->mm) */ 198 static struct kmem_cache *mm_cachep; 199 200 static void account_kernel_stack(struct thread_info *ti, int account) 201 { 202 struct zone *zone = page_zone(virt_to_page(ti)); 203 204 mod_zone_page_state(zone, NR_KERNEL_STACK, account); 205 } 206 207 void free_task(struct task_struct *tsk) 208 { 209 account_kernel_stack(tsk->stack, -1); 210 arch_release_thread_info(tsk->stack); 211 free_thread_info(tsk->stack); 212 rt_mutex_debug_task_free(tsk); 213 ftrace_graph_exit_task(tsk); 214 put_seccomp_filter(tsk); 215 arch_release_task_struct(tsk); 216 free_task_struct(tsk); 217 } 218 EXPORT_SYMBOL(free_task); 219 220 static inline void free_signal_struct(struct signal_struct *sig) 221 { 222 taskstats_tgid_free(sig); 223 sched_autogroup_exit(sig); 224 kmem_cache_free(signal_cachep, sig); 225 } 226 227 static inline void put_signal_struct(struct signal_struct *sig) 228 { 229 if (atomic_dec_and_test(&sig->sigcnt)) 230 free_signal_struct(sig); 231 } 232 233 void __put_task_struct(struct task_struct *tsk) 234 { 235 WARN_ON(!tsk->exit_state); 236 WARN_ON(atomic_read(&tsk->usage)); 237 WARN_ON(tsk == current); 238 239 security_task_free(tsk); 240 exit_creds(tsk); 241 delayacct_tsk_free(tsk); 242 put_signal_struct(tsk->signal); 243 244 if (!profile_handoff_task(tsk)) 245 free_task(tsk); 246 } 247 EXPORT_SYMBOL_GPL(__put_task_struct); 248 249 void __init __weak arch_task_cache_init(void) { } 250 251 void __init fork_init(unsigned long mempages) 252 { 253 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR 254 #ifndef ARCH_MIN_TASKALIGN 255 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 256 #endif 257 /* create a slab on which task_structs can be allocated */ 258 task_struct_cachep = 259 kmem_cache_create("task_struct", sizeof(struct task_struct), 260 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 261 #endif 262 263 /* do the arch specific task caches init */ 264 arch_task_cache_init(); 265 266 /* 267 * The default maximum number of threads is set to a safe 268 * value: the thread structures can take up at most half 269 * of memory. 270 */ 271 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 272 273 /* 274 * we need to allow at least 20 threads to boot a system 275 */ 276 if (max_threads < 20) 277 max_threads = 20; 278 279 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 280 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 281 init_task.signal->rlim[RLIMIT_SIGPENDING] = 282 init_task.signal->rlim[RLIMIT_NPROC]; 283 } 284 285 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 286 struct task_struct *src) 287 { 288 *dst = *src; 289 return 0; 290 } 291 292 static struct task_struct *dup_task_struct(struct task_struct *orig) 293 { 294 struct task_struct *tsk; 295 struct thread_info *ti; 296 unsigned long *stackend; 297 int node = tsk_fork_get_node(orig); 298 int err; 299 300 tsk = alloc_task_struct_node(node); 301 if (!tsk) 302 return NULL; 303 304 ti = alloc_thread_info_node(tsk, node); 305 if (!ti) 306 goto free_tsk; 307 308 err = arch_dup_task_struct(tsk, orig); 309 if (err) 310 goto free_ti; 311 312 tsk->stack = ti; 313 314 setup_thread_stack(tsk, orig); 315 clear_user_return_notifier(tsk); 316 clear_tsk_need_resched(tsk); 317 stackend = end_of_stack(tsk); 318 *stackend = STACK_END_MAGIC; /* for overflow detection */ 319 320 #ifdef CONFIG_CC_STACKPROTECTOR 321 tsk->stack_canary = get_random_int(); 322 #endif 323 324 /* 325 * One for us, one for whoever does the "release_task()" (usually 326 * parent) 327 */ 328 atomic_set(&tsk->usage, 2); 329 #ifdef CONFIG_BLK_DEV_IO_TRACE 330 tsk->btrace_seq = 0; 331 #endif 332 tsk->splice_pipe = NULL; 333 334 account_kernel_stack(ti, 1); 335 336 return tsk; 337 338 free_ti: 339 free_thread_info(ti); 340 free_tsk: 341 free_task_struct(tsk); 342 return NULL; 343 } 344 345 #ifdef CONFIG_MMU 346 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 347 { 348 struct vm_area_struct *mpnt, *tmp, *prev, **pprev; 349 struct rb_node **rb_link, *rb_parent; 350 int retval; 351 unsigned long charge; 352 struct mempolicy *pol; 353 354 down_write(&oldmm->mmap_sem); 355 flush_cache_dup_mm(oldmm); 356 /* 357 * Not linked in yet - no deadlock potential: 358 */ 359 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 360 361 mm->locked_vm = 0; 362 mm->mmap = NULL; 363 mm->mmap_cache = NULL; 364 mm->free_area_cache = oldmm->mmap_base; 365 mm->cached_hole_size = ~0UL; 366 mm->map_count = 0; 367 cpumask_clear(mm_cpumask(mm)); 368 mm->mm_rb = RB_ROOT; 369 rb_link = &mm->mm_rb.rb_node; 370 rb_parent = NULL; 371 pprev = &mm->mmap; 372 retval = ksm_fork(mm, oldmm); 373 if (retval) 374 goto out; 375 retval = khugepaged_fork(mm, oldmm); 376 if (retval) 377 goto out; 378 379 prev = NULL; 380 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 381 struct file *file; 382 383 if (mpnt->vm_flags & VM_DONTCOPY) { 384 long pages = vma_pages(mpnt); 385 mm->total_vm -= pages; 386 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 387 -pages); 388 continue; 389 } 390 charge = 0; 391 if (mpnt->vm_flags & VM_ACCOUNT) { 392 unsigned long len = vma_pages(mpnt); 393 394 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 395 goto fail_nomem; 396 charge = len; 397 } 398 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 399 if (!tmp) 400 goto fail_nomem; 401 *tmp = *mpnt; 402 INIT_LIST_HEAD(&tmp->anon_vma_chain); 403 pol = mpol_dup(vma_policy(mpnt)); 404 retval = PTR_ERR(pol); 405 if (IS_ERR(pol)) 406 goto fail_nomem_policy; 407 vma_set_policy(tmp, pol); 408 tmp->vm_mm = mm; 409 if (anon_vma_fork(tmp, mpnt)) 410 goto fail_nomem_anon_vma_fork; 411 tmp->vm_flags &= ~VM_LOCKED; 412 tmp->vm_next = tmp->vm_prev = NULL; 413 file = tmp->vm_file; 414 if (file) { 415 struct inode *inode = file->f_path.dentry->d_inode; 416 struct address_space *mapping = file->f_mapping; 417 418 get_file(file); 419 if (tmp->vm_flags & VM_DENYWRITE) 420 atomic_dec(&inode->i_writecount); 421 mutex_lock(&mapping->i_mmap_mutex); 422 if (tmp->vm_flags & VM_SHARED) 423 mapping->i_mmap_writable++; 424 flush_dcache_mmap_lock(mapping); 425 /* insert tmp into the share list, just after mpnt */ 426 vma_prio_tree_add(tmp, mpnt); 427 flush_dcache_mmap_unlock(mapping); 428 mutex_unlock(&mapping->i_mmap_mutex); 429 } 430 431 /* 432 * Clear hugetlb-related page reserves for children. This only 433 * affects MAP_PRIVATE mappings. Faults generated by the child 434 * are not guaranteed to succeed, even if read-only 435 */ 436 if (is_vm_hugetlb_page(tmp)) 437 reset_vma_resv_huge_pages(tmp); 438 439 /* 440 * Link in the new vma and copy the page table entries. 441 */ 442 *pprev = tmp; 443 pprev = &tmp->vm_next; 444 tmp->vm_prev = prev; 445 prev = tmp; 446 447 __vma_link_rb(mm, tmp, rb_link, rb_parent); 448 rb_link = &tmp->vm_rb.rb_right; 449 rb_parent = &tmp->vm_rb; 450 451 mm->map_count++; 452 retval = copy_page_range(mm, oldmm, mpnt); 453 454 if (tmp->vm_ops && tmp->vm_ops->open) 455 tmp->vm_ops->open(tmp); 456 457 if (retval) 458 goto out; 459 460 if (file && uprobe_mmap(tmp)) 461 goto out; 462 } 463 /* a new mm has just been created */ 464 arch_dup_mmap(oldmm, mm); 465 retval = 0; 466 out: 467 up_write(&mm->mmap_sem); 468 flush_tlb_mm(oldmm); 469 up_write(&oldmm->mmap_sem); 470 return retval; 471 fail_nomem_anon_vma_fork: 472 mpol_put(pol); 473 fail_nomem_policy: 474 kmem_cache_free(vm_area_cachep, tmp); 475 fail_nomem: 476 retval = -ENOMEM; 477 vm_unacct_memory(charge); 478 goto out; 479 } 480 481 static inline int mm_alloc_pgd(struct mm_struct *mm) 482 { 483 mm->pgd = pgd_alloc(mm); 484 if (unlikely(!mm->pgd)) 485 return -ENOMEM; 486 return 0; 487 } 488 489 static inline void mm_free_pgd(struct mm_struct *mm) 490 { 491 pgd_free(mm, mm->pgd); 492 } 493 #else 494 #define dup_mmap(mm, oldmm) (0) 495 #define mm_alloc_pgd(mm) (0) 496 #define mm_free_pgd(mm) 497 #endif /* CONFIG_MMU */ 498 499 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 500 501 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 502 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 503 504 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 505 506 static int __init coredump_filter_setup(char *s) 507 { 508 default_dump_filter = 509 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 510 MMF_DUMP_FILTER_MASK; 511 return 1; 512 } 513 514 __setup("coredump_filter=", coredump_filter_setup); 515 516 #include <linux/init_task.h> 517 518 static void mm_init_aio(struct mm_struct *mm) 519 { 520 #ifdef CONFIG_AIO 521 spin_lock_init(&mm->ioctx_lock); 522 INIT_HLIST_HEAD(&mm->ioctx_list); 523 #endif 524 } 525 526 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 527 { 528 atomic_set(&mm->mm_users, 1); 529 atomic_set(&mm->mm_count, 1); 530 init_rwsem(&mm->mmap_sem); 531 INIT_LIST_HEAD(&mm->mmlist); 532 mm->flags = (current->mm) ? 533 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; 534 mm->core_state = NULL; 535 mm->nr_ptes = 0; 536 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); 537 spin_lock_init(&mm->page_table_lock); 538 mm->free_area_cache = TASK_UNMAPPED_BASE; 539 mm->cached_hole_size = ~0UL; 540 mm_init_aio(mm); 541 mm_init_owner(mm, p); 542 543 if (likely(!mm_alloc_pgd(mm))) { 544 mm->def_flags = 0; 545 mmu_notifier_mm_init(mm); 546 return mm; 547 } 548 549 free_mm(mm); 550 return NULL; 551 } 552 553 static void check_mm(struct mm_struct *mm) 554 { 555 int i; 556 557 for (i = 0; i < NR_MM_COUNTERS; i++) { 558 long x = atomic_long_read(&mm->rss_stat.count[i]); 559 560 if (unlikely(x)) 561 printk(KERN_ALERT "BUG: Bad rss-counter state " 562 "mm:%p idx:%d val:%ld\n", mm, i, x); 563 } 564 565 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 566 VM_BUG_ON(mm->pmd_huge_pte); 567 #endif 568 } 569 570 /* 571 * Allocate and initialize an mm_struct. 572 */ 573 struct mm_struct *mm_alloc(void) 574 { 575 struct mm_struct *mm; 576 577 mm = allocate_mm(); 578 if (!mm) 579 return NULL; 580 581 memset(mm, 0, sizeof(*mm)); 582 mm_init_cpumask(mm); 583 return mm_init(mm, current); 584 } 585 586 /* 587 * Called when the last reference to the mm 588 * is dropped: either by a lazy thread or by 589 * mmput. Free the page directory and the mm. 590 */ 591 void __mmdrop(struct mm_struct *mm) 592 { 593 BUG_ON(mm == &init_mm); 594 mm_free_pgd(mm); 595 destroy_context(mm); 596 mmu_notifier_mm_destroy(mm); 597 check_mm(mm); 598 free_mm(mm); 599 } 600 EXPORT_SYMBOL_GPL(__mmdrop); 601 602 /* 603 * Decrement the use count and release all resources for an mm. 604 */ 605 void mmput(struct mm_struct *mm) 606 { 607 might_sleep(); 608 609 if (atomic_dec_and_test(&mm->mm_users)) { 610 uprobe_clear_state(mm); 611 exit_aio(mm); 612 ksm_exit(mm); 613 khugepaged_exit(mm); /* must run before exit_mmap */ 614 exit_mmap(mm); 615 set_mm_exe_file(mm, NULL); 616 if (!list_empty(&mm->mmlist)) { 617 spin_lock(&mmlist_lock); 618 list_del(&mm->mmlist); 619 spin_unlock(&mmlist_lock); 620 } 621 if (mm->binfmt) 622 module_put(mm->binfmt->module); 623 mmdrop(mm); 624 } 625 } 626 EXPORT_SYMBOL_GPL(mmput); 627 628 /* 629 * We added or removed a vma mapping the executable. The vmas are only mapped 630 * during exec and are not mapped with the mmap system call. 631 * Callers must hold down_write() on the mm's mmap_sem for these 632 */ 633 void added_exe_file_vma(struct mm_struct *mm) 634 { 635 mm->num_exe_file_vmas++; 636 } 637 638 void removed_exe_file_vma(struct mm_struct *mm) 639 { 640 mm->num_exe_file_vmas--; 641 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) { 642 fput(mm->exe_file); 643 mm->exe_file = NULL; 644 } 645 646 } 647 648 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) 649 { 650 if (new_exe_file) 651 get_file(new_exe_file); 652 if (mm->exe_file) 653 fput(mm->exe_file); 654 mm->exe_file = new_exe_file; 655 mm->num_exe_file_vmas = 0; 656 } 657 658 struct file *get_mm_exe_file(struct mm_struct *mm) 659 { 660 struct file *exe_file; 661 662 /* We need mmap_sem to protect against races with removal of 663 * VM_EXECUTABLE vmas */ 664 down_read(&mm->mmap_sem); 665 exe_file = mm->exe_file; 666 if (exe_file) 667 get_file(exe_file); 668 up_read(&mm->mmap_sem); 669 return exe_file; 670 } 671 672 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm) 673 { 674 /* It's safe to write the exe_file pointer without exe_file_lock because 675 * this is called during fork when the task is not yet in /proc */ 676 newmm->exe_file = get_mm_exe_file(oldmm); 677 } 678 679 /** 680 * get_task_mm - acquire a reference to the task's mm 681 * 682 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 683 * this kernel workthread has transiently adopted a user mm with use_mm, 684 * to do its AIO) is not set and if so returns a reference to it, after 685 * bumping up the use count. User must release the mm via mmput() 686 * after use. Typically used by /proc and ptrace. 687 */ 688 struct mm_struct *get_task_mm(struct task_struct *task) 689 { 690 struct mm_struct *mm; 691 692 task_lock(task); 693 mm = task->mm; 694 if (mm) { 695 if (task->flags & PF_KTHREAD) 696 mm = NULL; 697 else 698 atomic_inc(&mm->mm_users); 699 } 700 task_unlock(task); 701 return mm; 702 } 703 EXPORT_SYMBOL_GPL(get_task_mm); 704 705 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode) 706 { 707 struct mm_struct *mm; 708 int err; 709 710 err = mutex_lock_killable(&task->signal->cred_guard_mutex); 711 if (err) 712 return ERR_PTR(err); 713 714 mm = get_task_mm(task); 715 if (mm && mm != current->mm && 716 !ptrace_may_access(task, mode)) { 717 mmput(mm); 718 mm = ERR_PTR(-EACCES); 719 } 720 mutex_unlock(&task->signal->cred_guard_mutex); 721 722 return mm; 723 } 724 725 static void complete_vfork_done(struct task_struct *tsk) 726 { 727 struct completion *vfork; 728 729 task_lock(tsk); 730 vfork = tsk->vfork_done; 731 if (likely(vfork)) { 732 tsk->vfork_done = NULL; 733 complete(vfork); 734 } 735 task_unlock(tsk); 736 } 737 738 static int wait_for_vfork_done(struct task_struct *child, 739 struct completion *vfork) 740 { 741 int killed; 742 743 freezer_do_not_count(); 744 killed = wait_for_completion_killable(vfork); 745 freezer_count(); 746 747 if (killed) { 748 task_lock(child); 749 child->vfork_done = NULL; 750 task_unlock(child); 751 } 752 753 put_task_struct(child); 754 return killed; 755 } 756 757 /* Please note the differences between mmput and mm_release. 758 * mmput is called whenever we stop holding onto a mm_struct, 759 * error success whatever. 760 * 761 * mm_release is called after a mm_struct has been removed 762 * from the current process. 763 * 764 * This difference is important for error handling, when we 765 * only half set up a mm_struct for a new process and need to restore 766 * the old one. Because we mmput the new mm_struct before 767 * restoring the old one. . . 768 * Eric Biederman 10 January 1998 769 */ 770 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 771 { 772 /* Get rid of any futexes when releasing the mm */ 773 #ifdef CONFIG_FUTEX 774 if (unlikely(tsk->robust_list)) { 775 exit_robust_list(tsk); 776 tsk->robust_list = NULL; 777 } 778 #ifdef CONFIG_COMPAT 779 if (unlikely(tsk->compat_robust_list)) { 780 compat_exit_robust_list(tsk); 781 tsk->compat_robust_list = NULL; 782 } 783 #endif 784 if (unlikely(!list_empty(&tsk->pi_state_list))) 785 exit_pi_state_list(tsk); 786 #endif 787 788 uprobe_free_utask(tsk); 789 790 /* Get rid of any cached register state */ 791 deactivate_mm(tsk, mm); 792 793 /* 794 * If we're exiting normally, clear a user-space tid field if 795 * requested. We leave this alone when dying by signal, to leave 796 * the value intact in a core dump, and to save the unnecessary 797 * trouble, say, a killed vfork parent shouldn't touch this mm. 798 * Userland only wants this done for a sys_exit. 799 */ 800 if (tsk->clear_child_tid) { 801 if (!(tsk->flags & PF_SIGNALED) && 802 atomic_read(&mm->mm_users) > 1) { 803 /* 804 * We don't check the error code - if userspace has 805 * not set up a proper pointer then tough luck. 806 */ 807 put_user(0, tsk->clear_child_tid); 808 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 809 1, NULL, NULL, 0); 810 } 811 tsk->clear_child_tid = NULL; 812 } 813 814 /* 815 * All done, finally we can wake up parent and return this mm to him. 816 * Also kthread_stop() uses this completion for synchronization. 817 */ 818 if (tsk->vfork_done) 819 complete_vfork_done(tsk); 820 } 821 822 /* 823 * Allocate a new mm structure and copy contents from the 824 * mm structure of the passed in task structure. 825 */ 826 struct mm_struct *dup_mm(struct task_struct *tsk) 827 { 828 struct mm_struct *mm, *oldmm = current->mm; 829 int err; 830 831 if (!oldmm) 832 return NULL; 833 834 mm = allocate_mm(); 835 if (!mm) 836 goto fail_nomem; 837 838 memcpy(mm, oldmm, sizeof(*mm)); 839 mm_init_cpumask(mm); 840 841 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 842 mm->pmd_huge_pte = NULL; 843 #endif 844 uprobe_reset_state(mm); 845 846 if (!mm_init(mm, tsk)) 847 goto fail_nomem; 848 849 if (init_new_context(tsk, mm)) 850 goto fail_nocontext; 851 852 dup_mm_exe_file(oldmm, mm); 853 854 err = dup_mmap(mm, oldmm); 855 if (err) 856 goto free_pt; 857 858 mm->hiwater_rss = get_mm_rss(mm); 859 mm->hiwater_vm = mm->total_vm; 860 861 if (mm->binfmt && !try_module_get(mm->binfmt->module)) 862 goto free_pt; 863 864 return mm; 865 866 free_pt: 867 /* don't put binfmt in mmput, we haven't got module yet */ 868 mm->binfmt = NULL; 869 mmput(mm); 870 871 fail_nomem: 872 return NULL; 873 874 fail_nocontext: 875 /* 876 * If init_new_context() failed, we cannot use mmput() to free the mm 877 * because it calls destroy_context() 878 */ 879 mm_free_pgd(mm); 880 free_mm(mm); 881 return NULL; 882 } 883 884 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk) 885 { 886 struct mm_struct *mm, *oldmm; 887 int retval; 888 889 tsk->min_flt = tsk->maj_flt = 0; 890 tsk->nvcsw = tsk->nivcsw = 0; 891 #ifdef CONFIG_DETECT_HUNG_TASK 892 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 893 #endif 894 895 tsk->mm = NULL; 896 tsk->active_mm = NULL; 897 898 /* 899 * Are we cloning a kernel thread? 900 * 901 * We need to steal a active VM for that.. 902 */ 903 oldmm = current->mm; 904 if (!oldmm) 905 return 0; 906 907 if (clone_flags & CLONE_VM) { 908 atomic_inc(&oldmm->mm_users); 909 mm = oldmm; 910 goto good_mm; 911 } 912 913 retval = -ENOMEM; 914 mm = dup_mm(tsk); 915 if (!mm) 916 goto fail_nomem; 917 918 good_mm: 919 tsk->mm = mm; 920 tsk->active_mm = mm; 921 return 0; 922 923 fail_nomem: 924 return retval; 925 } 926 927 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 928 { 929 struct fs_struct *fs = current->fs; 930 if (clone_flags & CLONE_FS) { 931 /* tsk->fs is already what we want */ 932 spin_lock(&fs->lock); 933 if (fs->in_exec) { 934 spin_unlock(&fs->lock); 935 return -EAGAIN; 936 } 937 fs->users++; 938 spin_unlock(&fs->lock); 939 return 0; 940 } 941 tsk->fs = copy_fs_struct(fs); 942 if (!tsk->fs) 943 return -ENOMEM; 944 return 0; 945 } 946 947 static int copy_files(unsigned long clone_flags, struct task_struct *tsk) 948 { 949 struct files_struct *oldf, *newf; 950 int error = 0; 951 952 /* 953 * A background process may not have any files ... 954 */ 955 oldf = current->files; 956 if (!oldf) 957 goto out; 958 959 if (clone_flags & CLONE_FILES) { 960 atomic_inc(&oldf->count); 961 goto out; 962 } 963 964 newf = dup_fd(oldf, &error); 965 if (!newf) 966 goto out; 967 968 tsk->files = newf; 969 error = 0; 970 out: 971 return error; 972 } 973 974 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 975 { 976 #ifdef CONFIG_BLOCK 977 struct io_context *ioc = current->io_context; 978 struct io_context *new_ioc; 979 980 if (!ioc) 981 return 0; 982 /* 983 * Share io context with parent, if CLONE_IO is set 984 */ 985 if (clone_flags & CLONE_IO) { 986 ioc_task_link(ioc); 987 tsk->io_context = ioc; 988 } else if (ioprio_valid(ioc->ioprio)) { 989 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE); 990 if (unlikely(!new_ioc)) 991 return -ENOMEM; 992 993 new_ioc->ioprio = ioc->ioprio; 994 put_io_context(new_ioc); 995 } 996 #endif 997 return 0; 998 } 999 1000 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 1001 { 1002 struct sighand_struct *sig; 1003 1004 if (clone_flags & CLONE_SIGHAND) { 1005 atomic_inc(¤t->sighand->count); 1006 return 0; 1007 } 1008 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 1009 rcu_assign_pointer(tsk->sighand, sig); 1010 if (!sig) 1011 return -ENOMEM; 1012 atomic_set(&sig->count, 1); 1013 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 1014 return 0; 1015 } 1016 1017 void __cleanup_sighand(struct sighand_struct *sighand) 1018 { 1019 if (atomic_dec_and_test(&sighand->count)) { 1020 signalfd_cleanup(sighand); 1021 kmem_cache_free(sighand_cachep, sighand); 1022 } 1023 } 1024 1025 1026 /* 1027 * Initialize POSIX timer handling for a thread group. 1028 */ 1029 static void posix_cpu_timers_init_group(struct signal_struct *sig) 1030 { 1031 unsigned long cpu_limit; 1032 1033 /* Thread group counters. */ 1034 thread_group_cputime_init(sig); 1035 1036 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur); 1037 if (cpu_limit != RLIM_INFINITY) { 1038 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit); 1039 sig->cputimer.running = 1; 1040 } 1041 1042 /* The timer lists. */ 1043 INIT_LIST_HEAD(&sig->cpu_timers[0]); 1044 INIT_LIST_HEAD(&sig->cpu_timers[1]); 1045 INIT_LIST_HEAD(&sig->cpu_timers[2]); 1046 } 1047 1048 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 1049 { 1050 struct signal_struct *sig; 1051 1052 if (clone_flags & CLONE_THREAD) 1053 return 0; 1054 1055 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL); 1056 tsk->signal = sig; 1057 if (!sig) 1058 return -ENOMEM; 1059 1060 sig->nr_threads = 1; 1061 atomic_set(&sig->live, 1); 1062 atomic_set(&sig->sigcnt, 1); 1063 init_waitqueue_head(&sig->wait_chldexit); 1064 if (clone_flags & CLONE_NEWPID) 1065 sig->flags |= SIGNAL_UNKILLABLE; 1066 sig->curr_target = tsk; 1067 init_sigpending(&sig->shared_pending); 1068 INIT_LIST_HEAD(&sig->posix_timers); 1069 1070 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 1071 sig->real_timer.function = it_real_fn; 1072 1073 task_lock(current->group_leader); 1074 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 1075 task_unlock(current->group_leader); 1076 1077 posix_cpu_timers_init_group(sig); 1078 1079 tty_audit_fork(sig); 1080 sched_autogroup_fork(sig); 1081 1082 #ifdef CONFIG_CGROUPS 1083 init_rwsem(&sig->group_rwsem); 1084 #endif 1085 1086 sig->oom_adj = current->signal->oom_adj; 1087 sig->oom_score_adj = current->signal->oom_score_adj; 1088 sig->oom_score_adj_min = current->signal->oom_score_adj_min; 1089 1090 sig->has_child_subreaper = current->signal->has_child_subreaper || 1091 current->signal->is_child_subreaper; 1092 1093 mutex_init(&sig->cred_guard_mutex); 1094 1095 return 0; 1096 } 1097 1098 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 1099 { 1100 unsigned long new_flags = p->flags; 1101 1102 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER); 1103 new_flags |= PF_FORKNOEXEC; 1104 p->flags = new_flags; 1105 } 1106 1107 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 1108 { 1109 current->clear_child_tid = tidptr; 1110 1111 return task_pid_vnr(current); 1112 } 1113 1114 static void rt_mutex_init_task(struct task_struct *p) 1115 { 1116 raw_spin_lock_init(&p->pi_lock); 1117 #ifdef CONFIG_RT_MUTEXES 1118 plist_head_init(&p->pi_waiters); 1119 p->pi_blocked_on = NULL; 1120 #endif 1121 } 1122 1123 #ifdef CONFIG_MM_OWNER 1124 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 1125 { 1126 mm->owner = p; 1127 } 1128 #endif /* CONFIG_MM_OWNER */ 1129 1130 /* 1131 * Initialize POSIX timer handling for a single task. 1132 */ 1133 static void posix_cpu_timers_init(struct task_struct *tsk) 1134 { 1135 tsk->cputime_expires.prof_exp = 0; 1136 tsk->cputime_expires.virt_exp = 0; 1137 tsk->cputime_expires.sched_exp = 0; 1138 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 1139 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 1140 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 1141 } 1142 1143 /* 1144 * This creates a new process as a copy of the old one, 1145 * but does not actually start it yet. 1146 * 1147 * It copies the registers, and all the appropriate 1148 * parts of the process environment (as per the clone 1149 * flags). The actual kick-off is left to the caller. 1150 */ 1151 static struct task_struct *copy_process(unsigned long clone_flags, 1152 unsigned long stack_start, 1153 struct pt_regs *regs, 1154 unsigned long stack_size, 1155 int __user *child_tidptr, 1156 struct pid *pid, 1157 int trace) 1158 { 1159 int retval; 1160 struct task_struct *p; 1161 int cgroup_callbacks_done = 0; 1162 1163 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 1164 return ERR_PTR(-EINVAL); 1165 1166 /* 1167 * Thread groups must share signals as well, and detached threads 1168 * can only be started up within the thread group. 1169 */ 1170 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 1171 return ERR_PTR(-EINVAL); 1172 1173 /* 1174 * Shared signal handlers imply shared VM. By way of the above, 1175 * thread groups also imply shared VM. Blocking this case allows 1176 * for various simplifications in other code. 1177 */ 1178 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1179 return ERR_PTR(-EINVAL); 1180 1181 /* 1182 * Siblings of global init remain as zombies on exit since they are 1183 * not reaped by their parent (swapper). To solve this and to avoid 1184 * multi-rooted process trees, prevent global and container-inits 1185 * from creating siblings. 1186 */ 1187 if ((clone_flags & CLONE_PARENT) && 1188 current->signal->flags & SIGNAL_UNKILLABLE) 1189 return ERR_PTR(-EINVAL); 1190 1191 retval = security_task_create(clone_flags); 1192 if (retval) 1193 goto fork_out; 1194 1195 retval = -ENOMEM; 1196 p = dup_task_struct(current); 1197 if (!p) 1198 goto fork_out; 1199 1200 ftrace_graph_init_task(p); 1201 get_seccomp_filter(p); 1202 1203 rt_mutex_init_task(p); 1204 1205 #ifdef CONFIG_PROVE_LOCKING 1206 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1207 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1208 #endif 1209 retval = -EAGAIN; 1210 if (atomic_read(&p->real_cred->user->processes) >= 1211 task_rlimit(p, RLIMIT_NPROC)) { 1212 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1213 p->real_cred->user != INIT_USER) 1214 goto bad_fork_free; 1215 } 1216 current->flags &= ~PF_NPROC_EXCEEDED; 1217 1218 retval = copy_creds(p, clone_flags); 1219 if (retval < 0) 1220 goto bad_fork_free; 1221 1222 /* 1223 * If multiple threads are within copy_process(), then this check 1224 * triggers too late. This doesn't hurt, the check is only there 1225 * to stop root fork bombs. 1226 */ 1227 retval = -EAGAIN; 1228 if (nr_threads >= max_threads) 1229 goto bad_fork_cleanup_count; 1230 1231 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1232 goto bad_fork_cleanup_count; 1233 1234 p->did_exec = 0; 1235 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1236 copy_flags(clone_flags, p); 1237 INIT_LIST_HEAD(&p->children); 1238 INIT_LIST_HEAD(&p->sibling); 1239 rcu_copy_process(p); 1240 p->vfork_done = NULL; 1241 spin_lock_init(&p->alloc_lock); 1242 1243 init_sigpending(&p->pending); 1244 1245 p->utime = p->stime = p->gtime = 0; 1246 p->utimescaled = p->stimescaled = 0; 1247 #ifndef CONFIG_VIRT_CPU_ACCOUNTING 1248 p->prev_utime = p->prev_stime = 0; 1249 #endif 1250 #if defined(SPLIT_RSS_COUNTING) 1251 memset(&p->rss_stat, 0, sizeof(p->rss_stat)); 1252 #endif 1253 1254 p->default_timer_slack_ns = current->timer_slack_ns; 1255 1256 task_io_accounting_init(&p->ioac); 1257 acct_clear_integrals(p); 1258 1259 posix_cpu_timers_init(p); 1260 1261 do_posix_clock_monotonic_gettime(&p->start_time); 1262 p->real_start_time = p->start_time; 1263 monotonic_to_bootbased(&p->real_start_time); 1264 p->io_context = NULL; 1265 p->audit_context = NULL; 1266 if (clone_flags & CLONE_THREAD) 1267 threadgroup_change_begin(current); 1268 cgroup_fork(p); 1269 #ifdef CONFIG_NUMA 1270 p->mempolicy = mpol_dup(p->mempolicy); 1271 if (IS_ERR(p->mempolicy)) { 1272 retval = PTR_ERR(p->mempolicy); 1273 p->mempolicy = NULL; 1274 goto bad_fork_cleanup_cgroup; 1275 } 1276 mpol_fix_fork_child_flag(p); 1277 #endif 1278 #ifdef CONFIG_CPUSETS 1279 p->cpuset_mem_spread_rotor = NUMA_NO_NODE; 1280 p->cpuset_slab_spread_rotor = NUMA_NO_NODE; 1281 seqcount_init(&p->mems_allowed_seq); 1282 #endif 1283 #ifdef CONFIG_TRACE_IRQFLAGS 1284 p->irq_events = 0; 1285 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1286 p->hardirqs_enabled = 1; 1287 #else 1288 p->hardirqs_enabled = 0; 1289 #endif 1290 p->hardirq_enable_ip = 0; 1291 p->hardirq_enable_event = 0; 1292 p->hardirq_disable_ip = _THIS_IP_; 1293 p->hardirq_disable_event = 0; 1294 p->softirqs_enabled = 1; 1295 p->softirq_enable_ip = _THIS_IP_; 1296 p->softirq_enable_event = 0; 1297 p->softirq_disable_ip = 0; 1298 p->softirq_disable_event = 0; 1299 p->hardirq_context = 0; 1300 p->softirq_context = 0; 1301 #endif 1302 #ifdef CONFIG_LOCKDEP 1303 p->lockdep_depth = 0; /* no locks held yet */ 1304 p->curr_chain_key = 0; 1305 p->lockdep_recursion = 0; 1306 #endif 1307 1308 #ifdef CONFIG_DEBUG_MUTEXES 1309 p->blocked_on = NULL; /* not blocked yet */ 1310 #endif 1311 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 1312 p->memcg_batch.do_batch = 0; 1313 p->memcg_batch.memcg = NULL; 1314 #endif 1315 1316 /* Perform scheduler related setup. Assign this task to a CPU. */ 1317 sched_fork(p); 1318 1319 retval = perf_event_init_task(p); 1320 if (retval) 1321 goto bad_fork_cleanup_policy; 1322 retval = audit_alloc(p); 1323 if (retval) 1324 goto bad_fork_cleanup_policy; 1325 /* copy all the process information */ 1326 retval = copy_semundo(clone_flags, p); 1327 if (retval) 1328 goto bad_fork_cleanup_audit; 1329 retval = copy_files(clone_flags, p); 1330 if (retval) 1331 goto bad_fork_cleanup_semundo; 1332 retval = copy_fs(clone_flags, p); 1333 if (retval) 1334 goto bad_fork_cleanup_files; 1335 retval = copy_sighand(clone_flags, p); 1336 if (retval) 1337 goto bad_fork_cleanup_fs; 1338 retval = copy_signal(clone_flags, p); 1339 if (retval) 1340 goto bad_fork_cleanup_sighand; 1341 retval = copy_mm(clone_flags, p); 1342 if (retval) 1343 goto bad_fork_cleanup_signal; 1344 retval = copy_namespaces(clone_flags, p); 1345 if (retval) 1346 goto bad_fork_cleanup_mm; 1347 retval = copy_io(clone_flags, p); 1348 if (retval) 1349 goto bad_fork_cleanup_namespaces; 1350 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1351 if (retval) 1352 goto bad_fork_cleanup_io; 1353 1354 if (pid != &init_struct_pid) { 1355 retval = -ENOMEM; 1356 pid = alloc_pid(p->nsproxy->pid_ns); 1357 if (!pid) 1358 goto bad_fork_cleanup_io; 1359 } 1360 1361 p->pid = pid_nr(pid); 1362 p->tgid = p->pid; 1363 if (clone_flags & CLONE_THREAD) 1364 p->tgid = current->tgid; 1365 1366 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1367 /* 1368 * Clear TID on mm_release()? 1369 */ 1370 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; 1371 #ifdef CONFIG_BLOCK 1372 p->plug = NULL; 1373 #endif 1374 #ifdef CONFIG_FUTEX 1375 p->robust_list = NULL; 1376 #ifdef CONFIG_COMPAT 1377 p->compat_robust_list = NULL; 1378 #endif 1379 INIT_LIST_HEAD(&p->pi_state_list); 1380 p->pi_state_cache = NULL; 1381 #endif 1382 uprobe_copy_process(p); 1383 /* 1384 * sigaltstack should be cleared when sharing the same VM 1385 */ 1386 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1387 p->sas_ss_sp = p->sas_ss_size = 0; 1388 1389 /* 1390 * Syscall tracing and stepping should be turned off in the 1391 * child regardless of CLONE_PTRACE. 1392 */ 1393 user_disable_single_step(p); 1394 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1395 #ifdef TIF_SYSCALL_EMU 1396 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1397 #endif 1398 clear_all_latency_tracing(p); 1399 1400 /* ok, now we should be set up.. */ 1401 if (clone_flags & CLONE_THREAD) 1402 p->exit_signal = -1; 1403 else if (clone_flags & CLONE_PARENT) 1404 p->exit_signal = current->group_leader->exit_signal; 1405 else 1406 p->exit_signal = (clone_flags & CSIGNAL); 1407 1408 p->pdeath_signal = 0; 1409 p->exit_state = 0; 1410 1411 p->nr_dirtied = 0; 1412 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10); 1413 p->dirty_paused_when = 0; 1414 1415 /* 1416 * Ok, make it visible to the rest of the system. 1417 * We dont wake it up yet. 1418 */ 1419 p->group_leader = p; 1420 INIT_LIST_HEAD(&p->thread_group); 1421 p->task_works = NULL; 1422 1423 /* Now that the task is set up, run cgroup callbacks if 1424 * necessary. We need to run them before the task is visible 1425 * on the tasklist. */ 1426 cgroup_fork_callbacks(p); 1427 cgroup_callbacks_done = 1; 1428 1429 /* Need tasklist lock for parent etc handling! */ 1430 write_lock_irq(&tasklist_lock); 1431 1432 /* CLONE_PARENT re-uses the old parent */ 1433 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1434 p->real_parent = current->real_parent; 1435 p->parent_exec_id = current->parent_exec_id; 1436 } else { 1437 p->real_parent = current; 1438 p->parent_exec_id = current->self_exec_id; 1439 } 1440 1441 spin_lock(¤t->sighand->siglock); 1442 1443 /* 1444 * Process group and session signals need to be delivered to just the 1445 * parent before the fork or both the parent and the child after the 1446 * fork. Restart if a signal comes in before we add the new process to 1447 * it's process group. 1448 * A fatal signal pending means that current will exit, so the new 1449 * thread can't slip out of an OOM kill (or normal SIGKILL). 1450 */ 1451 recalc_sigpending(); 1452 if (signal_pending(current)) { 1453 spin_unlock(¤t->sighand->siglock); 1454 write_unlock_irq(&tasklist_lock); 1455 retval = -ERESTARTNOINTR; 1456 goto bad_fork_free_pid; 1457 } 1458 1459 if (clone_flags & CLONE_THREAD) { 1460 current->signal->nr_threads++; 1461 atomic_inc(¤t->signal->live); 1462 atomic_inc(¤t->signal->sigcnt); 1463 p->group_leader = current->group_leader; 1464 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1465 } 1466 1467 if (likely(p->pid)) { 1468 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); 1469 1470 if (thread_group_leader(p)) { 1471 if (is_child_reaper(pid)) 1472 p->nsproxy->pid_ns->child_reaper = p; 1473 1474 p->signal->leader_pid = pid; 1475 p->signal->tty = tty_kref_get(current->signal->tty); 1476 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1477 attach_pid(p, PIDTYPE_SID, task_session(current)); 1478 list_add_tail(&p->sibling, &p->real_parent->children); 1479 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1480 __this_cpu_inc(process_counts); 1481 } 1482 attach_pid(p, PIDTYPE_PID, pid); 1483 nr_threads++; 1484 } 1485 1486 total_forks++; 1487 spin_unlock(¤t->sighand->siglock); 1488 write_unlock_irq(&tasklist_lock); 1489 proc_fork_connector(p); 1490 cgroup_post_fork(p); 1491 if (clone_flags & CLONE_THREAD) 1492 threadgroup_change_end(current); 1493 perf_event_fork(p); 1494 1495 trace_task_newtask(p, clone_flags); 1496 1497 return p; 1498 1499 bad_fork_free_pid: 1500 if (pid != &init_struct_pid) 1501 free_pid(pid); 1502 bad_fork_cleanup_io: 1503 if (p->io_context) 1504 exit_io_context(p); 1505 bad_fork_cleanup_namespaces: 1506 if (unlikely(clone_flags & CLONE_NEWPID)) 1507 pid_ns_release_proc(p->nsproxy->pid_ns); 1508 exit_task_namespaces(p); 1509 bad_fork_cleanup_mm: 1510 if (p->mm) 1511 mmput(p->mm); 1512 bad_fork_cleanup_signal: 1513 if (!(clone_flags & CLONE_THREAD)) 1514 free_signal_struct(p->signal); 1515 bad_fork_cleanup_sighand: 1516 __cleanup_sighand(p->sighand); 1517 bad_fork_cleanup_fs: 1518 exit_fs(p); /* blocking */ 1519 bad_fork_cleanup_files: 1520 exit_files(p); /* blocking */ 1521 bad_fork_cleanup_semundo: 1522 exit_sem(p); 1523 bad_fork_cleanup_audit: 1524 audit_free(p); 1525 bad_fork_cleanup_policy: 1526 perf_event_free_task(p); 1527 #ifdef CONFIG_NUMA 1528 mpol_put(p->mempolicy); 1529 bad_fork_cleanup_cgroup: 1530 #endif 1531 if (clone_flags & CLONE_THREAD) 1532 threadgroup_change_end(current); 1533 cgroup_exit(p, cgroup_callbacks_done); 1534 delayacct_tsk_free(p); 1535 module_put(task_thread_info(p)->exec_domain->module); 1536 bad_fork_cleanup_count: 1537 atomic_dec(&p->cred->user->processes); 1538 exit_creds(p); 1539 bad_fork_free: 1540 free_task(p); 1541 fork_out: 1542 return ERR_PTR(retval); 1543 } 1544 1545 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1546 { 1547 memset(regs, 0, sizeof(struct pt_regs)); 1548 return regs; 1549 } 1550 1551 static inline void init_idle_pids(struct pid_link *links) 1552 { 1553 enum pid_type type; 1554 1555 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { 1556 INIT_HLIST_NODE(&links[type].node); /* not really needed */ 1557 links[type].pid = &init_struct_pid; 1558 } 1559 } 1560 1561 struct task_struct * __cpuinit fork_idle(int cpu) 1562 { 1563 struct task_struct *task; 1564 struct pt_regs regs; 1565 1566 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1567 &init_struct_pid, 0); 1568 if (!IS_ERR(task)) { 1569 init_idle_pids(task->pids); 1570 init_idle(task, cpu); 1571 } 1572 1573 return task; 1574 } 1575 1576 /* 1577 * Ok, this is the main fork-routine. 1578 * 1579 * It copies the process, and if successful kick-starts 1580 * it and waits for it to finish using the VM if required. 1581 */ 1582 long do_fork(unsigned long clone_flags, 1583 unsigned long stack_start, 1584 struct pt_regs *regs, 1585 unsigned long stack_size, 1586 int __user *parent_tidptr, 1587 int __user *child_tidptr) 1588 { 1589 struct task_struct *p; 1590 int trace = 0; 1591 long nr; 1592 1593 /* 1594 * Do some preliminary argument and permissions checking before we 1595 * actually start allocating stuff 1596 */ 1597 if (clone_flags & CLONE_NEWUSER) { 1598 if (clone_flags & CLONE_THREAD) 1599 return -EINVAL; 1600 /* hopefully this check will go away when userns support is 1601 * complete 1602 */ 1603 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1604 !capable(CAP_SETGID)) 1605 return -EPERM; 1606 } 1607 1608 /* 1609 * Determine whether and which event to report to ptracer. When 1610 * called from kernel_thread or CLONE_UNTRACED is explicitly 1611 * requested, no event is reported; otherwise, report if the event 1612 * for the type of forking is enabled. 1613 */ 1614 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) { 1615 if (clone_flags & CLONE_VFORK) 1616 trace = PTRACE_EVENT_VFORK; 1617 else if ((clone_flags & CSIGNAL) != SIGCHLD) 1618 trace = PTRACE_EVENT_CLONE; 1619 else 1620 trace = PTRACE_EVENT_FORK; 1621 1622 if (likely(!ptrace_event_enabled(current, trace))) 1623 trace = 0; 1624 } 1625 1626 p = copy_process(clone_flags, stack_start, regs, stack_size, 1627 child_tidptr, NULL, trace); 1628 /* 1629 * Do this prior waking up the new thread - the thread pointer 1630 * might get invalid after that point, if the thread exits quickly. 1631 */ 1632 if (!IS_ERR(p)) { 1633 struct completion vfork; 1634 1635 trace_sched_process_fork(current, p); 1636 1637 nr = task_pid_vnr(p); 1638 1639 if (clone_flags & CLONE_PARENT_SETTID) 1640 put_user(nr, parent_tidptr); 1641 1642 if (clone_flags & CLONE_VFORK) { 1643 p->vfork_done = &vfork; 1644 init_completion(&vfork); 1645 get_task_struct(p); 1646 } 1647 1648 wake_up_new_task(p); 1649 1650 /* forking complete and child started to run, tell ptracer */ 1651 if (unlikely(trace)) 1652 ptrace_event(trace, nr); 1653 1654 if (clone_flags & CLONE_VFORK) { 1655 if (!wait_for_vfork_done(p, &vfork)) 1656 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr); 1657 } 1658 } else { 1659 nr = PTR_ERR(p); 1660 } 1661 return nr; 1662 } 1663 1664 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1665 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1666 #endif 1667 1668 static void sighand_ctor(void *data) 1669 { 1670 struct sighand_struct *sighand = data; 1671 1672 spin_lock_init(&sighand->siglock); 1673 init_waitqueue_head(&sighand->signalfd_wqh); 1674 } 1675 1676 void __init proc_caches_init(void) 1677 { 1678 sighand_cachep = kmem_cache_create("sighand_cache", 1679 sizeof(struct sighand_struct), 0, 1680 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1681 SLAB_NOTRACK, sighand_ctor); 1682 signal_cachep = kmem_cache_create("signal_cache", 1683 sizeof(struct signal_struct), 0, 1684 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1685 files_cachep = kmem_cache_create("files_cache", 1686 sizeof(struct files_struct), 0, 1687 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1688 fs_cachep = kmem_cache_create("fs_cache", 1689 sizeof(struct fs_struct), 0, 1690 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1691 /* 1692 * FIXME! The "sizeof(struct mm_struct)" currently includes the 1693 * whole struct cpumask for the OFFSTACK case. We could change 1694 * this to *only* allocate as much of it as required by the 1695 * maximum number of CPU's we can ever have. The cpumask_allocation 1696 * is at the end of the structure, exactly for that reason. 1697 */ 1698 mm_cachep = kmem_cache_create("mm_struct", 1699 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1700 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1701 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1702 mmap_init(); 1703 nsproxy_cache_init(); 1704 } 1705 1706 /* 1707 * Check constraints on flags passed to the unshare system call. 1708 */ 1709 static int check_unshare_flags(unsigned long unshare_flags) 1710 { 1711 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1712 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1713 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1714 return -EINVAL; 1715 /* 1716 * Not implemented, but pretend it works if there is nothing to 1717 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND 1718 * needs to unshare vm. 1719 */ 1720 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) { 1721 /* FIXME: get_task_mm() increments ->mm_users */ 1722 if (atomic_read(¤t->mm->mm_users) > 1) 1723 return -EINVAL; 1724 } 1725 1726 return 0; 1727 } 1728 1729 /* 1730 * Unshare the filesystem structure if it is being shared 1731 */ 1732 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1733 { 1734 struct fs_struct *fs = current->fs; 1735 1736 if (!(unshare_flags & CLONE_FS) || !fs) 1737 return 0; 1738 1739 /* don't need lock here; in the worst case we'll do useless copy */ 1740 if (fs->users == 1) 1741 return 0; 1742 1743 *new_fsp = copy_fs_struct(fs); 1744 if (!*new_fsp) 1745 return -ENOMEM; 1746 1747 return 0; 1748 } 1749 1750 /* 1751 * Unshare file descriptor table if it is being shared 1752 */ 1753 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1754 { 1755 struct files_struct *fd = current->files; 1756 int error = 0; 1757 1758 if ((unshare_flags & CLONE_FILES) && 1759 (fd && atomic_read(&fd->count) > 1)) { 1760 *new_fdp = dup_fd(fd, &error); 1761 if (!*new_fdp) 1762 return error; 1763 } 1764 1765 return 0; 1766 } 1767 1768 /* 1769 * unshare allows a process to 'unshare' part of the process 1770 * context which was originally shared using clone. copy_* 1771 * functions used by do_fork() cannot be used here directly 1772 * because they modify an inactive task_struct that is being 1773 * constructed. Here we are modifying the current, active, 1774 * task_struct. 1775 */ 1776 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1777 { 1778 struct fs_struct *fs, *new_fs = NULL; 1779 struct files_struct *fd, *new_fd = NULL; 1780 struct nsproxy *new_nsproxy = NULL; 1781 int do_sysvsem = 0; 1782 int err; 1783 1784 err = check_unshare_flags(unshare_flags); 1785 if (err) 1786 goto bad_unshare_out; 1787 1788 /* 1789 * If unsharing namespace, must also unshare filesystem information. 1790 */ 1791 if (unshare_flags & CLONE_NEWNS) 1792 unshare_flags |= CLONE_FS; 1793 /* 1794 * CLONE_NEWIPC must also detach from the undolist: after switching 1795 * to a new ipc namespace, the semaphore arrays from the old 1796 * namespace are unreachable. 1797 */ 1798 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1799 do_sysvsem = 1; 1800 err = unshare_fs(unshare_flags, &new_fs); 1801 if (err) 1802 goto bad_unshare_out; 1803 err = unshare_fd(unshare_flags, &new_fd); 1804 if (err) 1805 goto bad_unshare_cleanup_fs; 1806 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs); 1807 if (err) 1808 goto bad_unshare_cleanup_fd; 1809 1810 if (new_fs || new_fd || do_sysvsem || new_nsproxy) { 1811 if (do_sysvsem) { 1812 /* 1813 * CLONE_SYSVSEM is equivalent to sys_exit(). 1814 */ 1815 exit_sem(current); 1816 } 1817 1818 if (new_nsproxy) { 1819 switch_task_namespaces(current, new_nsproxy); 1820 new_nsproxy = NULL; 1821 } 1822 1823 task_lock(current); 1824 1825 if (new_fs) { 1826 fs = current->fs; 1827 spin_lock(&fs->lock); 1828 current->fs = new_fs; 1829 if (--fs->users) 1830 new_fs = NULL; 1831 else 1832 new_fs = fs; 1833 spin_unlock(&fs->lock); 1834 } 1835 1836 if (new_fd) { 1837 fd = current->files; 1838 current->files = new_fd; 1839 new_fd = fd; 1840 } 1841 1842 task_unlock(current); 1843 } 1844 1845 if (new_nsproxy) 1846 put_nsproxy(new_nsproxy); 1847 1848 bad_unshare_cleanup_fd: 1849 if (new_fd) 1850 put_files_struct(new_fd); 1851 1852 bad_unshare_cleanup_fs: 1853 if (new_fs) 1854 free_fs_struct(new_fs); 1855 1856 bad_unshare_out: 1857 return err; 1858 } 1859 1860 /* 1861 * Helper to unshare the files of the current task. 1862 * We don't want to expose copy_files internals to 1863 * the exec layer of the kernel. 1864 */ 1865 1866 int unshare_files(struct files_struct **displaced) 1867 { 1868 struct task_struct *task = current; 1869 struct files_struct *copy = NULL; 1870 int error; 1871 1872 error = unshare_fd(CLONE_FILES, ©); 1873 if (error || !copy) { 1874 *displaced = NULL; 1875 return error; 1876 } 1877 *displaced = task->files; 1878 task_lock(task); 1879 task->files = copy; 1880 task_unlock(task); 1881 return 0; 1882 } 1883